Main lug versus main breaker

Reply

  #1  
Old 11-16-14, 04:51 AM
chandler's Avatar
Banned. Rule And/Or Policy Violation
Thread Starter
Join Date: Dec 2005
Location: USA
Posts: 39,968
Main lug versus main breaker

I have an odd situation. We are building a 48 x 30 garage for a client with 2 16' doors and man door for his car collection. Normally I would run a circuit of say 60 amps to a main breaker panel in the garage for distribution. He is insisting on not having anything but lights and a few receptacles. I plan on installing 12 fluorescent lights, 2 carriage lights and a dozen or so receptacles.

Would it be feasible to run this off his abandoned spa location, changing the breaker there to 30 amps and installing a main lug box in the garage with capacity of 4 breakers or less? That way I can run 10 THWN in 2" conduit to the main lug and distribute it via 14 and 12 nm to the lights and receptacles. Run is about 75 feet.

Or would I need a main breaker panel to do this? I want to make it possible for a future owner to increase capacity if needed by running the 2" conduit, but satisfy this client for his immediate needs.
 
Sponsored Links
  #2  
Old 11-16-14, 06:54 AM
pcboss's Avatar
Forum Topic Moderator
Join Date: Jul 2002
Location: Maryland
Posts: 14,594
With only four circuits you can do this with a main lug. The only advantage I see is that you can use the #10 vs larger wire that would be more future proof. The small panel could have a backed main installed later, but might require the panel to be changed.

IMO I would install a larger panel with a main breaker.
 
  #3  
Old 11-16-14, 08:06 AM
Tolyn Ironhand's Avatar
Group Moderator
Join Date: Nov 2007
Location: Twin Cities, MN
Posts: 12,285
Maybe I missed it, but is this an attached or detached garage?

With a separate building you can have up to 6 disconnects (breakers) in a panel before you need a main. However, the cost difference between an 6 circuit panel and one with a main breaker is only about $20 so it really doesn't make much sense to install such a small panel.

Are you going to use the spa feed? If so I would keep the same feed rather then changing the breaker.
 
  #4  
Old 11-16-14, 10:58 AM
chandler's Avatar
Banned. Rule And/Or Policy Violation
Thread Starter
Join Date: Dec 2005
Location: USA
Posts: 39,968
It is a detached garage. I haven't been able to find breaker mains less than 100 amps. Keeping the same feed from the spa would entail running #6, which is viable, but a little more expensive. Dropping it down to 30 amps was the only way I could see using the #10 wires. I am using 2" conduit to keep it from being future proof, so someone could run larger wires if they desired more out there. I'm wide open for suggestions, and thanks.
 
  #5  
Old 11-16-14, 11:21 AM
pcboss's Avatar
Forum Topic Moderator
Join Date: Jul 2002
Location: Maryland
Posts: 14,594
A 100 amp main is the smallest you will find without needing to backfeed a two pole and add a hold down kit. It does not need to match the service panel breaker that feeds the panel. It is just a disconnect.
 

Last edited by pcboss; 11-16-14 at 11:53 AM.
  #6  
Old 11-16-14, 11:28 AM
ray2047's Avatar
Group Moderator
Join Date: Mar 2006
Location: USA
Posts: 33,058
A #10 may be too small to fit a 100 amp breaker but you can just pigtail larger wire to the #10. Cost advantage of the main breaker panel may be if you get the kit it will come with several branch circuit breakers.
 
  #7  
Old 11-16-14, 11:51 AM
chandler's Avatar
Banned. Rule And/Or Policy Violation
Thread Starter
Join Date: Dec 2005
Location: USA
Posts: 39,968
OK, may go with a 100 amp small panel with breaker, protect it from the spa with a 30 amp breaker, run 10 THWN in the 2" conduit to supply the panel using the 100 amp main as a disconnect, then branch off to the lights and receptacles. I saw one of the kits with 4 breakers and the main for about $70, so it is a pretty good deal. At least the 2" conduit will help for future expansion. Thanks for all the input.
 
  #8  
Old 11-16-14, 02:09 PM
Member
Join Date: Mar 2006
Location: Wet side of Washington state.
Posts: 18,399
Have you considered just a 20 ampere multi-wire branch circuit from the spa panel? That way no CB panel at all need be used, just a local disconnect which could be a $10 A/C disconnect. You could even run the #10 conductors and use a fused A/C disconnect with 20 ampere fuses.
 
  #9  
Old 11-16-14, 02:19 PM
chandler's Avatar
Banned. Rule And/Or Policy Violation
Thread Starter
Join Date: Dec 2005
Location: USA
Posts: 39,968
Joel, I'll run that past the inspector. It is feasible, however.
 
  #10  
Old 11-16-14, 04:08 PM
CasualJoe's Avatar
Member
Join Date: Jan 2010
Location: USA
Posts: 9,397
Chandler, if you haven't run the conduit yet, I see no reason to run conduit bigger than 1 inch from the spa location. The biggest wire you could use from there is just #6 anyway.
 
  #11  
Old 11-16-14, 05:10 PM
chandler's Avatar
Banned. Rule And/Or Policy Violation
Thread Starter
Join Date: Dec 2005
Location: USA
Posts: 39,968
Yeah, I haven't run it yet. The concrete guy stubbed in a 2" elbow in the slab, but I guess I could use a bushing and save a little money on that end, too. I was just future proofing it in case he, or the future owner, called for me to run a decent service to the location. 2" would do that.
 
  #12  
Old 11-16-14, 08:03 PM
CasualJoe's Avatar
Member
Join Date: Jan 2010
Location: USA
Posts: 9,397
Well, you could still run 1" PVC through the 2" elbow. Just heat a piece of 1" PVC till it gets floppy and shove it through. Problem solved.
 
Reply

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread
Display Modes